Syringe

ABSTRACT

A needleless syringe for injecting an injection objective substance into an injection target area of a living body is provided. The syringe includes an enclosing unit enclosing the injection objective substance, and an ignition device including an ignition charge and flowing an ignition current so that the ignition charge is combusted. The syringe also includes a pressurizing unit pressurizing the injection objective substance, and a flow passage unit defining a flow passage so that the pressurized injection objective substance is allowed to inject to the injection target area. The pressurizing unit raises a pressure applied to the injection objective substance to a peak pressure for the injection objective substance to penetrate through a surface of the injection target area and then lowers the pressure applied to the injection objective substance to a waiting pressure within 2 msec after the ignition current was allowed to flow to the ignition device.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57. Thefollowing application is incorporated herein by reference in itsentirety:

Title application Ser. No. Date Filed SYRINGE 15/694,633 Sep. 1, 2017

TECHNICAL FIELD

The described technology generally relates to a syringe (injector) withwhich an injection objective substance is injected into an injectiontarget area of a living body without using any injection needle.

BACKGROUND TECHNOLOGY

In relation to a needle-free syringe (needleless syringe) with which theinjection is performed without using any injection needle, aconstruction is adopted in some cases such that an injection componentis injected or allowed to inject by applying a pressure to anaccommodating chamber in which an injection solution is accommodated, bymeans of a pressurized gas or a spring. However, in the case of theneedle-free syringe having the conventionally known construction, thereproducibility is unsatisfactory in relation to the depth and theinjection amount of the injection solution. Therefore, it is difficultto affirm that such a needle-free syringe generally comes intowidespread use.

Accordingly, such a technique is disclosed that a propellant charge,which is composed of a mixture of two types of powders, i.e., a highspeed combustion powder and a low speed combustion powder, is utilizedto adjust the output pressure (injection pressure) for the injectionsolution in a plurality of levels or stages (see, for example,JP2003-534839). Specifically, the injection solution is firstly allowedto inject by applying a large force to a piston by the combustion of thehigh speed combustion powder. As a result, the injection solutionpenetrates through a skin of a human body or the like, and the injectionsolution is fed into the body. After that, a pressure is continuouslyapplied to such an extent that the injection solution can be diffused inthe skin by the combustion of the low speed combustion powder.

U.S. Pat. No. 2,704,542 discloses such a technique that an injectionsolution is administered in two stages by using a needle-free syringe.In this technique, the injection solution is allowed to inject byapplying a high pressure thereto so that the injection solutionpenetrates into the skin, and then the pressure, which is applied to theinjection solution, is lowered so that it is contemplated to dispersethe injection solution in the skin. Further, United States PatentPublication No. 2006/0258986 discloses such a technique that theinjection pressure for an injection solution is adjusted by theintensity of the electric current by using a magnet and a coil. In thistechnique, the injection pressure is adjusted so that a high pressure isfirstly applied in order that the injection solution penetrates throughthe skin, and then an approximately constant pressure is provided inorder that the desired injection solution is fed or delivered.

The pressure, which is applied to the injection solution when theneedle-free syringe is used, is variously adjusted not only for such apurpose that the injection solution is allowed to arrive at the interiorof the skin but also for other purposes other than the above. Forexample, in United States Patent Publication No. 2005/0010168, such adescription is found that the increase in the pressure applied to theinjection solution is unfavorable after the penetration through the skinin order to mitigate the noise generated when the injection solution isallowed to inject by using a pressurized gas.

In this context, the target, for which the injection is performed byusing the needle-free syringe, is the living body such as the human bodyor the like in many cases. Accordingly, a discussion is provided inrelation to the behavior of an injected solution with respect to a gelagent generally used for an experiment and the skin of the living body(see, for example, Joy Baxter, Samir Mitragotri, “Jet-induced skinpuncture and its impact on needle-free jet injections: Experimentalstudies and a predictive model”, Journal of Controlled Release (U.S.A.)106 (2005), p 361-373). This discussion refers, for example, to acorrelation between a depth of a hole formed by the injection and a holedepth having a maximum dispersion width, and a correlation between theYoung's modulus of the skin and the hole depth. Further, JoySchramm-Baxter, Samir Mitragotri, “Needle-free jet injections:dependence of jet penetration and dispersion in the skin on jet power”,Journal of Controlled Release (U.S.A.) 97 (2004), p 527-535 refers to acorrelation between the dispersion width of an injection solution in thehuman skin and the nozzle diameter of a needle-free syringe.

SUMMARY Problem to be Solved

When the injection is performed for the living body, the component whichis contained in the injection solution and the depth in the injectiontarget area of the living body into which the component is to be feddiffer depending on the purpose of the injection. This is because theinjection target area of the living body includes various structuressuch as skin, muscle, internal organs and the like, and the biologicaltissues, which constitute the structures, have different functionsdepending on the depths from the surface (surface on which the syringeis brought in contact with the structure when the injection isperformed), and because it becomes difficult to appropriately exhibitthe effect if the component contained in the injection solution does notarrive at the objective biological tissue.

For example, the human skin can be distinguished or classified intoepidermis, dermis, and subcutaneous tissue (hypodermis) in a layeredform from the surface side. Further, the epidermis can be distinguishedor classified into horny cell layer and intradermis. In order that therespective layers perform the respective functions anatomically, thehorny cell layer is composed of keratinocytes, the intradermis iscomposed of dendritic cells and pigment cells, the dermis is composed offibroblasts and collagen cells, and the subcutaneous tissue is composedof subcutaneous fat and the like. When an injection solution is injectedfor a predetermined purpose, it is preferable that the predeterminedcomponent contained therein is precisely delivered, for example, to theobjective tissue.

In order that the injection objective substance is efficiently injectedwithout a leakage when the injection objective substance is injectedinto the injection target area of the living body, it is necessary thatthe pressure, which is applied to the injection objective substance,should be appropriately controlled from the start to the end of theinjection. That is, if the injection speed (velocity) of the injectionobjective substance, which is brought about by the pressurization, istoo slow, the substance is rebounded by the skin. To the contrary, ifthe injection speed (velocity) is too fast, then the injection depth canbe secured in the injection target area, but the injection speed exceedsan injection speed which is adequate to diffuse the substance in thearea. Therefore, it is considered that the injection objective substanceis rebounded due to the excessive supply, and it is difficult tocontemplate the appropriate diffusion thereof. Taking the foregoingproblem into consideration, an object of the present invention is toprovide a syringe which makes it possible to feed an injection objectivesubstance into an objective injection target area of a living bodywithout using any injection needle so that the injection objectivesubstance can be widely diffused at a depth.

Solution for the Problem

In order to solve the problem as described above, the present inventionadopts the following construction. That is, the pressure, which isapplied to an injection objective substance in order to allow theinjection objective substance to inject, is adjusted in accordance withpressurizing modes having mutually different characteristics in relationto a syringe for injecting the injection objective substance into aninjection target area of a living body without using any injectionneedle. Owing to the different pressurizing modes, the injectionobjective substance can be fed into a biological tissue at a desireddepth in the injection target area.

Specifically, the present invention provides a syringe for injecting aninjection objective substance into an injection target area of a livingbody without using any injection needle; the syringe including anenclosing unit which encloses the injection objective substance; apressurizing unit which pressurizes the injection objective substanceenclosed in the enclosing unit; and a flow passage unit which defines aflow passage so that the injection objective substance, which ispressurized by the pressurizing unit, is allowed to discharge to theinjection target area. The pressurizing unit generates a firstpressurizing mode in which a pressure applied to the injection objectivesubstance in the pressurizing unit is raised to a first peak pressure inorder to allow the injection objective substance to penetrate through asurface of the injection target area, and then the pressure applied tothe injection objective substance is lowered to a waiting pressure; anda second pressurizing mode in which the injection objective substancehaving the waiting pressure is pressurized so that the pressure appliedto the injection objective substance is raised to a second peak pressureto inject a predetermined injection amount of the injection objectivesubstance.

In the syringe according to the present invention, the injectionobjective substance, which is to be injected into the injection targetarea of the living body, is enclosed in the enclosing unit, and thepressure is applied to the injection objective substance enclosed in theenclosing unit. Thus, the movement of the injection objective substanceis prompted. As a result, the injection objective substance is allowedto discharge to the injection target area while passing through the flowpassage unit. The injection objective substance contains a component oringredient which is expected to exhibit any efficacy at the inside ofthe injection target area. As described above, the pressure applied inthe pressurizing unit is the driving source when the injection objectivesubstance is allowed to inject. Therefore, any enclosing state of theinjection objective substance in the enclosing unit or any physical formfor the injection objective substance such as liquid, fluid in a gelform, powder, solid in a granular form in the enclosing unit isavailable as long as that the injection objective substance can beallowed to inject by being pressurized in the pressurizing unit.

For example, the injection objective substance may be a liquid or solidin a gel form, provided that the fluidity, which makes it possible toallow the injection objective substance to inject, is secured orguaranteed. Further, the component, which is to be fed into theinjection target area of the living body, is contained in the injectionobjective substance. The component may exist in such a state that thecomponent is dissolved in the injection objective substance, or thecomponent may be in such a state that the component is simply mixedwithout being dissolved. For example, the component to be fed includes,for example, vaccine for enhancing antibody, protein for beauty, andcultured cells for regenerating hair. The injection objective substanceis formed by containing the component in a liquid or a fluid in a gelform or the like so that the component as described above can be allowedto inject.

Further, as for the pressurizing source to pressurize the injectionobjective substance by the pressurizing unit, it is possible to utilizea variety of pressurizing sources, provided that the pressurizing formsor modes of the first pressurizing mode and the second pressurizing modedescribed above can be used. The pressurizing source is exemplified, forexample, by those which utilize the elastic force brought about by aspring or the like, those which utilize the pressurized gas, those whichutilize the combustion of any explosive charge, and those which utilizean electric actuator (for example, a motor, a piezoelectric element orthe like) for effecting the pressurization.

In this construction, the injection objective substance can beadequately injected into the injection target area of the living bodyowing to the two pressurizing modes realized by the pressurizing unit.In other words, when the first pressurizing mode and the secondpressurizing mode are adopted, then the injection objective substance isfed to the objective injection depth of the injection target area suchas the skin structure or the like, and the injection objective substanceis diffused. In the first pressurizing mode, the pressure applied to theinjection objective substance is raised to the first peak pressure, andthen the pressure is lowered to the waiting pressure. Accordingly, theinjection objective substance firstly penetrates through the surface ofthe injection target area of the living body, and the injectionobjective substance advances in the depth direction of the area.

The injection energy of the injection objective substance is determinedby the flow rate of the substance allowed to inject per unit time.Therefore, the larger the pressurizing speed (velocity) for theinjection objective substance (amount of pressure increase per unittime) in the first pressurizing mode is, the deeper the injection depthbrought about by the injection objective substance in the firstpressurizing mode is. In the first pressurizing mode, the pressureincrease is adjusted so that at least the pressure, which is required topenetrate through the surface of the injection target area, is appliedto the injection objective substance.

In this context, the applicant assumes the following mechanism for theinjection into the injection target area, of the injection objectivesubstance allowed to inject. It is not intended that the presentapplicant is restricted by this mechanism. It is considered that anyother invention, which provides the effect that is the same as orequivalent to the effect of the present application as a result of theexecution of the pressure control with respect to the injectionobjective substance as described in the present application, belongs tothe category of the present invention, even if the other inventionfollows any mechanism different from the mechanism.

When the injection objective substance is allowed to discharge to theinjection target area, then the forward end of the flow (jet flow) ofthe pressurized injection objective substance allowed to discharge atthe early stage cuts out the injection target area, and the cutfragments are lifted upwardly by the back flow. Accordingly, a hole isbored, and the forward end of the jet flow advances in the depthdirection. As the forward end of the jet flow is deepened, the injectionenergy, which is possessed by the jet flow, is lost by the friction withthe back flow. When the injection energy is lost by the back flow, andthe ability to cut out the injection target area is lost, i.e., when theinjection energy is balanced with the resistance energy of the backflow, then the advance of the hole depth is stopped.

When the jet flow is provided into the injection target area, the sameamount of the back flow comes upwardly in the opposite direction in thehole. Therefore, it is necessary that the hole diameter should besecured in order to allow the back flow to flow therethrough. However,the biological tissue, which is the injection target area, intrinsicallyhas the elasticity, and hence the biological tissue has such a tendencythat the biological tissue is contracted or shrunk to decrease the holediameter. The contractile force (shrinkage force) narrows the back flowpassage (reduces the diameter). Therefore, when such a state is giventhat the contractile force is relatively large with respect to the jetflow, then the resistance, which is brought about by the back flow, isincreased, and the injection energy possessed by the jet flow isbalanced at a relatively shallow position.

Taking the foregoing mechanism into consideration, the present inventionis considered as follows. That is, when the pressure, which is appliedto the injection objective substance, is raised to the first peakpressure, and the pressure is thereafter lowered to the waitingpressure, then the elastic force, which is intrinsically possessed bythe injection target area of the living body, is relatively large ascompared with the jet flow at a part of the penetrating passage (forwardend portion of the penetrating passage) of the injection objectivesubstance formed to arrive at a certain injection depth. Therefore, itis considered that the diameter of the penetrating passage is reduced.In this situation, it is considered that the forward end portion of theinjection objective substance that is subjected to the pressurereduction to the waiting pressure, is in such a state that the pressure(waiting pressure) applied to the injection objective substance isgenerally balanced with the pressure brought about by the back flow fromthe injection target area of the living body, at such a position thatthe injection target area of the living body, which is positioned at theforward end portion of the penetrating passage having the reduceddiameter, is not reached. It is considered that when the diameter isreduced at the part of the penetrating passage as described above, thestrength against the jet flow is raised as compared with any portionwhich is not subjected to the reduction of the diameter. The increase inthe strength means that it is difficult to secure the back flow routewhen the pressurization is performed again in the second pressurizingmode. Therefore, even when the pressurization is performed again inaccordance with the second pressurizing mode after the arrival at thewaiting pressure, the jet flow does not reach the forward end of thepenetrating passage, because the area, through which the back flowpasses, is lost in the contracted or shrunk penetrating passage, whereinthe pressurization is principally effected for the injection objectivesubstance existing in the portion of the penetrating passage notsubjected to the diameter reduction. Therefore, the permeation of theinjection objective substance is facilitated in the direction in whichthe injection objective substance is spread in the injection area of theliving body, rather than the penetrating passage is further elongated inthe depth direction. Thus, the injection objective substance is diffusedin a wide range. In a way, it is also affirmed that the firstpressurizing mode, which is provided until arrival at the waitingpressure, is the step which makes it possible to form such a state thatthe diffusion is to be performed, and the second pressurizing mode isthe step which accelerates the diffusion of the injection objectivesubstance in the formed state. In the second pressurizing mode, thepressure applied to the injection objective substance is raised to thesecond peak pressure, and thus it is possible to realize the injectionof the injection objective substance in an objective predeterminedinjection amount.

The first peak pressure and the waiting pressure in the firstpressurizing mode described above and the second peak pressure in thesecond pressurizing mode are appropriately determined depending on thepurpose of the injection of the injection objective substance. In thiscontext, it is also appropriate to consider the physical property of theinjection target area of the living body as the target, for example, theYoung's modulus or the like of the skin. The living body, which is theinjection target of the syringe according to the present invention, isnot limited to human, which may be, for example, a farm animal such aspig or a pet such as dog.

As described above, according to the syringe according to the presentinvention, the injection objective substance undergoes the waitingpressure when the mode transitions from the first pressurizing mode tothe second pressurizing mode. Thus, it is possible to effectivelycontemplate the diffusion of the injection objective substance in theinjection target area without uselessly deepening the injection depth.That is, the syringe according to the present invention makes itpossible to widely diffuse the injection objective substance at arelatively shallow depth in the injection target area of the livingbody.

In the syringe as described above, it is also preferable that thewaiting pressure is not more than a first predetermined ratio of thefirst peak pressure. The present applicant found out the fact that theeffective diffusion of the injection objective substance as describedabove can be realized when the ratio of the waiting pressure withrespect to the first peak pressure is not more than the firstpredetermined ratio. Preferably, for example, the first predeterminedratio is set to 60%.

In the syringe as described above, it is also preferable that the secondpeak pressure is not more than the first peak pressure; and a pressuredifference between the first peak pressure and the second peak pressureis within a second predetermined ratio with respect to the first peakpressure. That is, the second peak pressure is not more than the firstpeak pressure. However, the pressure difference therebetween issuppressed so that the pressure difference does not exceed the secondpredetermined ratio on the basis of the first peak pressure.Accordingly, it is possible to realize the injection in an objectiveinjection amount in the second pressurizing mode without uselesslydeepening the injection depth.

On the other hand, in the syringe as described above, it is alsopreferable that the second peak pressure is a pressure which exceeds thefirst peak pressure. In accordance with the mechanism assumed asdescribed above, even when the second peak pressure exceeds the firstpeak pressure, then the effective diffusion of the injection objectivesubstance is facilitated after the injection objective substance oncearrives at the waiting pressure, and it is possible to suppress anyuseless increase in the injection depth. The injection with the desiredamount is easily realized in the second pressurizing mode in some casesby raising the second peak pressure as described above depending on thephysical property or characteristic of the injection target area of theliving body.

In the syringe as described above, it is also preferable that a rate ofpressure increase from the waiting pressure to the second peak pressurein the second pressurizing mode is set to be lower than a rate ofpressure increase from start of pressurization to the first peakpressure in the first pressurizing mode. Accordingly, the pressureundergoes the waiting pressure in the first pressurizing mode, and thusit is possible to realize the effective diffusion of the injectionobjective substance.

It is also preferable that an amount of the injection objectivesubstance in the second pressurizing mode is set to be larger than anamount of the injection objective substance in the first pressurizingmode. It is considered that most of the injection objective substance,which is allowed to inject in the first pressurizing mode until arrivalat the waiting pressure, is subjected to the hole formation (boring) inthe injection target area in order to form the state appropriate todiffuse the injection objective substance in the injection target areaas described above, and the injection objective substance is generallydischarged as the back flow to the outside of the injection target area.In view of the above, when the injection amount is relatively increasedin the second pressurizing mode as described above, then a larger amountof the injection objective substance can be diffused to the objectivedepth of the injection target area, and it is expected to exhibit theeffect of the component or ingredient contained in the injectionobjective substance.

In this context, in the syringe as described above, it is alsopreferable that the syringe further comprises an ignition device whichincludes an ignition charge; and a combustion chamber into which acombustion product produced by combustion of the ignition charge isallowed to flow and which accommodates a gas generating agent that is tobe combusted by the combustion product to produce a predetermined gas;wherein the syringe is constructed so that a pressure in the combustionchamber is applied to the injection objective substance enclosed in theenclosing unit. Further, in this construction, the pressurizing unituses an increase in pressure generated by the combustion of the ignitioncharge in the ignition device as a pressurization transition untilarrival at the first peak pressure in the first pressurizing mode; andan increase in pressure brought about by the predetermined gas producedby the gas generating agent as a pressurization transition until arrivalat the second peak pressure in the second pressurizing mode.

That is, the form or mode, in which the pressure produced by thecombustion of the explosive charge is utilized as the driving source forallowing the injection objective substance to be discharged, can beadopted as a specified example in order to realize the pressurizationapplied to the injection objective substance in accordance with thefirst pressurizing mode and the second pressurizing mode as describedabove. In the case of the syringe constructed as described above, it ispossible to preferably adjust the pressure transition in the firstpressurizing mode and the pressure transition in the second pressurizingmode by appropriately adjusting the respective components of the gasgenerating agent and the ignition charge for the ignition device, therespective shapes in the syringe, and the relative arrangementrelationship therebetween. The exemplary description of the drivingsource based on the use of the explosive charge as described above doesnot include any intention to exclude the adoption of any driving sourcebased on any other form or mode. For example, it is also allowable toadopt, as the driving source as described above, those which utilize theelastic force brought about by a spring or the like, those which utilizethe pressurized gas, and those which utilize an electric actuator (forexample, a motor, a piezoelectric element or the like) in order toeffect the pressurization.

In the syringe as described above, it is also preferable that a decreasein pressure, which is brought about by condensation of the combustionproduct in the combustion chamber in the first pressurizing mode, isused as a depressurization transition from the first peak pressure tothe waiting pressure. The condensation action of the combustion productis utilized for the decrease in pressure, and thus it is possible tosuppress the kinetic energy possessed by the injection objectivesubstance until arrival at the waiting pressure, while maintaining theenergy for penetrating through the surface of the injection target areaof the living body. It is possible to perform the injection at ashallower portion of the injection target area of the living body.

In the syringe as described above, it is also preferable that acombustion completion time of the ignition charge comes earlier than acombustion completion time of the gas generating agent; and a velocityof production of the gas from the gas generating agent is increased at astage at which the combustion of the ignition charge is completed andthe pressure applied to the injection objective substance is decreasedfrom the first peak pressure to the waiting pressure. That is, it isalso allowable that the combustion period of the ignition charge and thecombustion period of the gas generating agent are partially overlappedwith each other, provided that the waiting pressure can be secured inthe first pressurizing mode described above. When the combustion periodsare overlapped, then the pressure brought about by the combustion of theignition charge is superimposed on the pressure of the produced gasproduced from the gas generating agent, and the resultant pressure isapplied to the injection objective substance. In order to adjust thecombustion completion times of the ignition charge and the gasgenerating agent as described above, it is possible to change therespective compositions and the composition ratios. Even when the bothhave the same composition and the composition ratio, it is alsoallowable to change the respective shapes and dimensions (sizes). Forexample, when the state of the explosive charge is powdery, thecombustion completion time comes earlier than the combustion completiontime of an explosive charge having the same composition formed in a formof lump. Further, the combustion completion time can be also adjusted bychanging both of the composition and the shape and the dimension (size).In this way, even when the explosive charges having the same compositionare contained in the ignition charge and the gas generating agent, it ispossible to adjust the respective combustion completion times byadjusting, for example, the state, the shape, and the dimension (size)of each of the explosive charges.

In the syringe as described above, it is also preferable that theignition charge is any one of explosive charges of an explosive chargecontaining zirconium and potassium perchlorate, an explosive chargecontaining titanium hydride and potassium perchlorate, an explosivecharge containing titanium and potassium perchlorate, an explosivecharge containing aluminum and potassium perchlorate, an explosivecharge containing aluminum and bismuth oxide, an explosive chargecontaining aluminum and molybdenum oxide, an explosive charge containingaluminum and copper oxide, and an explosive charge containing aluminumand iron oxide, or an explosive charge composed of a combination of aplurality of the foregoing explosive charges. The ignition charges asdescribed above have the following feature. That is, the combustionproduct does not contain any gas component at the ordinary temperatureeven when any gas is produced in a high temperature state. Therefore,when the combustion product is brought in contact with the surface inthe combustion chamber, the condensation occurs immediately. Therefore,it is possible to perform the injection at a shallower portion of theinjection target area of the living body.

It is possible to feed the injection objective substance to the depth ofthe objective injection target area of the living body without using anyinjection needle so that the injection objective substance can be widelydiffused at the depth brought about thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A, FIG. 1B and FIG. 1C show a schematic arrangement of a syringeaccording to embodiments of the present invention.

FIG. 2 shows a schematic arrangement of an initiator (ignition device)installed to the syringe shown in FIGS. 1A-1C.

FIG. 3 schematically shows the skin structure of human.

FIG. 4 shows the transition of the pressure applied to the injectionsolution in the syringe shown in FIGS. 1A-1C.

FIG. 5A and FIG. 5B show a situation in which the injection solution isdiffused in the skin structure of human when the pressure, which is inthe transition as shown in FIG. 4, is applied to the injection solution.

FIG. 6A shows a first view illustrating a result of an injectionexperiment by using the syringe according to embodiments of the presentinvention.

FIG. 6B shows a second view illustrating a result of an injectionexperiment by using the syringe according to embodiments of the presentinvention.

FIG. 6C shows a third view illustrating a result of an injectionexperiment by using the syringe according to embodiments of the presentinvention.

DETAILED DESCRIPTION

A syringe 1 according to an embodiment of the present invention will beexplained below with reference to the drawings. The construction of thefollowing embodiment is described by way of example. The presentinvention is not limited to the construction of the embodiment.

In this embodiment, FIG. 1A shows a sectional view illustrating thesyringe 1, FIG. 1B shows a side view illustrating the syringe 1 asviewed from a side of an initiator 20, and FIG. 1C shows a side viewillustrating the syringe 1 as viewed from a side of nozzles 4 forallowing an injection solution to inject. The syringe 1 has a mainsyringe body 2. A through-hole 14, which extends in the axial directionand which has a constant diameter in the axial direction, is provided ata central portion of the main syringe body 2. One end of thethrough-hole 14 is communicated with a combustion chamber 9 which has adiameter that is larger than the diameter of the through-hole 14. Theremaining other end reaches the side of a nozzle hole 5 in which thenozzles 4 are formed. Further, the initiator 20 is installed on the sideopposite to the communicated portion of the combustion chamber 9communicated with the through-hole 14 so that the ignition unit thereofis opposed to the communicated portion.

An example of the initiator 20 will now be explained on the basis ofFIG. 2. The initiator 20 is an electric ignition device. A space forarranging an ignition charge 22 is defined in a cup 21 by the cup 21having a surface covered with an insulating cover. A metal header 24 isarranged in the space, and a cylindrical charge holder 23 is provided onan upper surface thereof. The ignition charge 22 is held by the chargeholder 23. A bridge wire 26, which electrically connects one conductivepin 28 and the metal header 24, is wired at the bottom portion of theignition charge 22. Two conductive pins 28 are fixed to the metal header24 with an insulator 25 intervening therebetween so that they are in amutually insulated state when no voltage is applied. Further, an openingof the cup 21, from which the two conductive pins 28 supported by theinsulator 25 extend, is protected by a resin 27 in a state in which theinsulation performance is maintained to be satisfactory between the twoconductive pins 28.

In the initiator 20 constructed as described above, when the voltage isapplied between the two conductive pins 28 by an external power source,then the current flows through the bridge wire 26, and the ignitioncharge 22 is combusted thereby. In this situation, the combustionproduct, which is produced by the combustion of the ignition charge 22,is spouted from the opening of the charge holder 23. Accordingly, in thepresent invention, the relative positional relationship of the initiator20 with respect to the main syringe body 2 is designed so that thecombustion product of the ignition charge 22, which is produced in theinitiator 20, flows into the combustion chamber 9. Further, an initiatorcap 12 is formed to have a brim-shaped cross section so that theinitiator cap 12 is hooked by the outer surface of the initiator 20, andthe initiator cap 12 is screw-fixed to the main syringe body 2.Accordingly, the initiator 20 is fixed to the main syringe body 2 bymeans of the initiator cap 12. Thus, the initiator 20 itself can beprevented from being disengaged from the main syringe body 2, whichwould be otherwise disengaged by the pressure brought about upon theignition in the initiator 20.

The ignition charge 22, which is used for the syringe 1, is preferablyexemplified by an explosive charge (ZPP) containing zirconium andpotassium perchlorate, an explosive charge (THPP) containing titaniumhydride and potassium perchlorate, an explosive charge (TiPP) containingtitanium and potassium perchlorate, an explosive charge (APP) containingaluminum and potassium perchlorate, an explosive charge (ABO) containingaluminum and bismuth oxide, an explosive charge (AMO) containingaluminum and molybdenum oxide, an explosive charge (ACO) containingaluminum and copper oxide, and an explosive charge (AFO) containingaluminum and iron oxide, or an explosive charge composed of acombination of a plurality of the foregoing explosive charges. Theexplosive charges as described above exhibit such a characteristic thatthe plasma having a high temperature and a high pressure is generatedduring the combustion immediately after the ignition, but the generatedpressure is suddenly lowered because no gas component is contained whenthe ordinary temperature is given and the combustion product iscondensed. This characteristic is the characteristic which preferablycontributes to the formation of the pressurizing mode for the injectionsolution in the syringe 1 according to the present invention, and thisfeature will be described later on. Any explosive charge other than theabove may be used as the ignition charge provided that the pressurizingmode can be realized as described later on.

In this embodiment, a gas generating agent 30 having a columnar shape,which is combusted by the combustion product produced by the combustionof the ignition charge 22 to produce the gas, is arranged in thecombustion chamber 9. The gas generating agent 30 is exemplified, forexample, by a single base smokeless propellant composed of 98% by massof nitrocellulose, 0.8% by mass of diphenylamine, and 1.2% by mass ofpotassium sulfate by way of example. It is also possible to use variousgas generating agents used for a gas generator for an airbag and a gasgenerator for a seat belt pretensioner. Unlike the ignition charge 22described above, in the case of the gas generating agent 30, thepredetermined gas, which is produced during the combustion, contains thegas component even at the ordinary temperature. Therefore, the rate ofdecrease in the generated pressure is extremely small as compared withthe ignition charge 22 described above. Further, the combustioncompletion time upon the combustion of the gas generating agent 30 isextremely long as compared with the ignition charge 22 described above.However, it is possible to change the combustion completion time of thegas generating agent 30 by adjusting the dimension, the size, and/or theshape, especially the surface shape of the gas generating agent 30 whenthe gas generating agent 30 is arranged in the combustion chamber 9.This is because the contact state, which is provided with respect to thecombustion product of the ignition charge 22 allowed to flow into thecombustion chamber 9, is considered to be changed depending on thesurface shape of the gas generating agent 30 and the relative positionalrelationship between the gas generating agent 30 and the ignition charge22 resulting from the arrangement of the gas generating agent 30 in thecombustion chamber 9.

In the next place, a piston 6 made of metal is arranged in thethrough-hole 14 so that the piston 6 is slidable in the axial directionin the through-hole 14. One end thereof is exposed to the side of thecombustion chamber 9, and a sealing member 7 is integrally attached tothe other end. An injection solution ML, which is the injectionobjective substance to be injected from the syringe 1, is enclosed in aspace formed in the through-hole 14 between the sealing member 7 andanother sealing member 8. Therefore, the enclosing unit of the syringeaccording to the present invention is formed by the sealing members 7, 8and the through-hole 14. Each of the sealing members 7, 8 is made ofrubber having the surface thinly coated with silicon oil so that theinjection solution does not leak when the injection solution ML isenclosed, and the injection solution ML can be smoothly moved in thethrough-hole 14 in accordance with the sliding movement of the piston 6.

In this embodiment, a flow passage unit of the syringe 1 according tothe present invention is formed on the forward end side of the syringe 1(right side as viewed in FIGS. 1A-1C). Specifically, a holder 5, whichis formed with nozzles 4 for allowing the injection solution ML toinject, is provided on the forward end side of the syringe 1. The holder5 is fixed to the end surface of the main syringe body 2 with a gasket 3intervening therebetween by the aid of a holder cap 13. The holder cap13 is formed to have a brim-shaped cross section so that the holder cap13 fixes the holder 5, and the holder cap 13 is screw-fixed to the mainsyringe body 2. Accordingly, the holder 5 is prevented from beingdisengaged from the main syringe body 2 by the pressure applied to theinjection solution ML when the injection solution ML is allowed toinject.

A recess 10, which can accommodate the sealing member 8, is formed at aportion opposed to the sealing member 8 in a state in which the holder 5is attached to the main syringe body 2. The recess 10 has approximatelythe same diameter as that of the sealing member 8, and the recess 10 hasa depth which is slightly longer than the length of the sealing member8. Accordingly, when the pressure is applied to the piston 6, and theinjection solution ML is moved to the forward end side of the syringe 1together with the sealing members 7, 8, then the sealing member 8 can beaccommodated in the recess 10. When the sealing member 8 is accommodatedin the recess 10, the pressurized injection solution ML is released.Thus, a flow passage 11 is formed at a portion of the holder 5 broughtin contact with the side of the main syringe body 2 so that the releasedinjection solution ML is guided to the nozzle 4. Accordingly, thereleased injection solution ML passes through the flow passage 11, andthe injection solution ML is allowed to discharge from the nozzle 4 tothe injection target. Owing to the fact that the recess 10 has the depthfor accommodating the sealing member 8, any inhibition of the injectionof the injection solution ML, which would be otherwise caused by thesealing member 8, can be avoided.

A plurality of nozzles 4 may be formed for the holder 5. Alternatively,one nozzle 4 may be formed. When the plurality of nozzles is formed, theflow passages, which correspond to the respective nozzles, are formed sothat the released injection solution is fed to the respective nozzles.Further, when the plurality of nozzles 4 is formed, as shown in FIG. 1C,it is preferable that the respective nozzles are arranged at equalintervals around the central axis of the syringe 1. In this embodiment,the three nozzles 4, which are provided for the holder 5, are arrangedat equal intervals around the central axis of the syringe 1. Thediameter of the nozzle 4 is appropriately set while considering, forexample, the injection target, the injection pressure applied to theinjection solution ML, and the physical property (viscosity) of theinjection solution.

In the syringe 1 constructed as described above, the combustion productor the predetermined gas is generated in the combustion chamber 9 bymeans of the ignition charge 22 provided in the initiator 20 and the gasgenerating agent 30 arranged in the combustion chamber 9 so that thepressure is applied to the injection solution ML enclosed in thethrough-hole 14 by the aid of the piston 6. As a result, the injectionsolution ML is pushed or extruded to the forward end side of the syringe1 together with the sealing members 7, 8. When the sealing member 8 isaccommodated in the recess 10, then the injection solution ML passesthrough the flow passage 11 and the nozzles 4, and the injectionsolution ML is allowed to inject to the injection target. The pressureis applied to the injection solution ML allowed to inject. Therefore,the injection solution ML penetrates through the surface of theinjection target, and the injection solution ML arrives at the insidethereof. Accordingly, it is possible to achieve the purpose of theinjection with the syringe 1.

In this embodiment, the injection target of the syringe 1 according tothe present invention is the skin structure of the living body such ashuman, farm animal or the like. This specification principally refers tothe action of the syringe 1 exerted on the human skin. Therefore, FIG. 3schematically shows an anatomical structure of the human skin. The humanskin is constructed in a layered form including epidermis, dermis,subcutaneous tissue (hypodermis), and muscular tissue as disposed in thedepth direction from the side of the skin surface. Further, theepidermis can be distinguished or classified into horny cell layer andintradermis in a layered form. In each of the layers of the skinstructure, the tissue and the main cells or the like for constructingthe tissue have different features as well.

Specifically, the horny cell layer is principally composed ofkeratinocytes, and the horny cell layer is positioned on the outermostsurface side of the skin. Therefore, the horny cell layer has thefunction of the so-called barrier layer. In general, the thickness ofthe horny cell layer is about 0.01 to 0.015 mm, and the horny cell layerperforms the surface protection for human by keratinocytes. Therefore,in order to physically insulate the interior of the human body from theexternal environment to some extent, a relatively high strength isrequired as well. On the other hand, the intradermis is constructed toinclude dendritic cells (Langerhans cells) and pigment cells(melanocytes). The epidermis is formed by the horny cell layer and theintradermis. The thickness of the epidermis is generally about 0.1 to 2mm. It is considered that the dendritic cells in the intradermis arecells which participate in the antigen-antibody reaction. This isbecause the dendritic cells recognize the presence of the antigen byincorporating the antigen, and the antigen-antibody reaction, in whichlymphocytes are activated to play a role to attach the foreign matter,tends to be induced. On the other hand, the pigment cells in theintradermis have the function to avoid the influence of the ultravioletlight radiated from the external environment.

In the next place, vessels and capillary vessels on the skin arecomplicatedly spread all over the dermis. Further, for example, sweatglands for adjusting the body temperature, hair roots of body hair(including hair on the head), and sebaceous glands associated therewithalso exist in the dermis. The dermis is the layer which makescommunication between the epidermis and the interior of the human body(subcutaneous tissue and muscular tissue). The dermis is constructed toinclude fibroblasts and collagen cells. Therefore, the state of thedermis greatly participates, for example, in the hair falling out andthe appearance of wrinkles due to the so-called collagen shortage or theelastin shortage.

In this way, the skin structure of human is generally formed in thelayered form. The intrinsic anatomical function is exhibited, forexample, by the cells and the tissue principally contained in each ofthe layers. This means the fact that it is desirable to inject acomponent (ingredient) for a medical treatment to a place (depth) of theskin structure in conformity with the purpose of the medical treatment,for example, when the medical treatment is applied to the skin. Forexample, the dendritic cells exist in the intradermis. Therefore, when avaccine injection is performed therein, it is possible to expect a moreeffective antigen-antibody reaction. However, in the case of theconventional injection technique, it is difficult to perform the vaccineinjection with respect to the intradermis which is positioned at therelatively shallow portion. Even when such a vaccine injection isperformed, the injection greatly depends on the skill of a health careworker or medical professional. Further, the pigment cells exist in theintradermis, and hence it is also demanded that when a beauty treatmentis performed for the so-called skin whitening, a specified component(ingredient) for the skin whitening is injected into the intradermis.However, in the case of the conventional technique, it is difficult toperform such a treatment as described above.

In the next place, fibroblasts and collagen cells exist in the dermis.Therefore, for example, if protein for removing skin wrinkles, enzyme,vitamin, amino acid, mineral, sugar, nucleic acid, and various growthfactors (epithelial cells and fibroblasts) are injected into the dermis,an effective beauty treatment effect is expected. However, the dermis isalso positioned at the relatively shallow portion in the same manner asthe intradermis. Therefore, in the case of the conventional technique,it is difficult to perform the beauty treatment by means of theinjection in many cases. As for a hair regeneration treatment, the hairroots are positioned in the dermis. Therefore, in order to perform thehair regeneration treatment, the following procedure is considered to befavorable. That is, for example, a stem cell injection method, in whichdermal papilla cells and/or epidermal stem cells are autologous culturedand cultured cells are autologous transplanted to the scalp, isperformed, or several types of growth factors and/or nutrient componentsextracted from stem cells are injected into a portion positioned in thevicinity of the dermis.

In this way, the substance, which is injected in accordance with thepurpose of the treatment for the skin, individually corresponds to theposition (depth) in the skin structure into which the substance isdesirably injected. However, it is difficult for the conventionaltechnique to adjust the injection position. In the case of the syringe 1according to the present invention, the depth, at which the injectionsolution arrives in the skin structure, can be preferably adjusted byadjusting the pressure applied to the injection solution. As describedabove, various substances (injection objective substances) are used tobe injected into the skin structure depending on the purpose of thetreatment thereof. Therefore, the injection objective substance isgenerally referred to as “injection solution” in the followingdescription. However, this includes no intention to limit the form andthe contents of the substance to be injected. As for the injectionobjective substance, the component (ingredient), which is to bedelivered to the skin structure, may be either dissolved or notdissolved. Any specified form is also available for the injectionobjective substance provided that the injection objective substance canbe allowed to inject to the skin structure from the nozzle 4 by beingpressurized. It is possible to adopt various forms including, forexample, liquid and gel forms.

For example, the injection objective substance usable in the beautytreatment is exemplified, for example, by protein for skin whitening orfor removing wrinkles, enzyme, vitamin, amino acid, mineral, sugar,nucleic acid, and various growth factors (epithelial cells andfibroblasts). Further, the injection objective substance in the hairregeneration treatment is exemplified, for example, by dermal papillacell, hair root stem cell, epidermal stem cell, HARG cocktail, and hairfor transplantation.

In the next place, an explanation will be made on the basis of FIG. 4about the specified pressurizing form for the injection solution asperformed in the syringe 1. FIG. 4 shows the pressure transition appliedto the injection solution enclosed in the through-hole 14 by the aid ofthe piston 6 by appropriately adjusting the combination of the ignitioncharge 22 and the gas generating agent 30 contained in the syringe 1.The horizontal axis of FIG. 4 represents the elapsed time inmillisecond, and the vertical axis represents the applied pressure inMPa. The pressure can be measured by installing a pressure gauge in apressure measuring port (not shown in FIGS. 1A-1C) provided to makecommunication with the combustion chamber 9 in the main syringe body 2.In the example shown in FIG. 4, the pressure transitions, which areprovided when three types of amounts of the gas generating agent 30 arecombined with the same amount of ZPP (containing zirconium and potassiumperchlorate) as the ignition charge 22, are shown as L1, L2, L3 in FIG.4.

An explanation will now be made about the pressure transitions L1 to L3in the syringe 1 according to the present invention. The pressuretransitions involve the common technical feature. At first, the commontechnical feature will be explained on the basis of the pressuretransition L2. In the pressure transition in the present invention, thecombustion of the ignition charge 22 is started immediately after theapplication of the electricity to the initiator 20, and thus thepressure suddenly arrives at the first peak pressure value P1max fromthe state in which the pressure is zero. After that, the pressure islowered to the waiting pressure Pw2 (the waiting pressure is representedby Pw1 in the pressure transition L1, and the waiting pressure isrepresented by the waiting pressure Pw3 in the pressure transition L3).The process, in which the pressure is applied to the injection solutionin accordance with the pressure transition as provided until arrival atthis point, is referred to as “first pressurizing mode”. After that, thepressure is raised again, and the pressure arrives at the second peakpressure P2max2 (the second peak pressure is represented by P2max1 inthe pressure transition L1, and the second peak pressure is representedby P2max3 in the pressure transition L3). After that, the pressure isgently lowered. The process or step, in which the pressure is applied tothe injection solution in accordance with the pressure transition forraising the pressure from the waiting pressure to the second peakpressure, is referred to as “second pressurizing mode”. In this way,each of the pressure transitions L1 to L3 is constructed by the firstpressurizing mode and the second pressurizing mode.

The two different pressurizing modes, which are provided in one pressuretransition as described above, are realized by the ignition charge 22and the gas generating agent 30 which have the different combustionmodes or forms. That is, the feature of the combustion form of theignition charge 22 resides in the instantaneous combustion brought aboutby the application of the electricity to the initiator 20. Further, whenthe produced combustion gas is condensed at the ordinary temperature, nogas component is contained therein, as represented by ZPP. Therefore,the pressure, which is applied to the injection solution, is suddenlylowered. Therefore, the pressure transition, which is based on the firstpressurizing mode, is completed in a minute time Δt shown in FIG. 4. Onthe other hand, the combustion product having the high temperature,which is produced by the combustion of the ignition charge 22, flowsinto the combustion chamber 9, and the gas generating agent 30 arrangedtherein is combusted thereby. Accordingly, the combustion of the gasgenerating agent 30 is started. Therefore, the gas generating agent 30is combusted during the pressure transition based on the firstpressurizing mode or immediately after the completion of the firstpressurizing mode, and the predetermined gas is produced thereby. Thevelocity of the generation of the gas from the gas generating agent 30is extremely gentle as compared with the velocity of the generation ofthe combustion product from the ignition charge 22. In other words, thecombustion completion time of the gas generating agent 30 is longer thanthe combustion completion time of the ignition charge 22. Therefore, asclarified from FIG. 4 as well, the pressure transition is depicted suchthat the pressure increase rate, which is provided from the waitingpressure Pw2 until arrival at the second peak pressure P2max2, isgentler than the pressure increase rate which is provided upon theignition of the ignition charge 22. This feature is provided in the samemanner for the pressure transitions L1, L3 as well.

An explanation will be made on the basis of FIG. 5A and FIG. 5B aboutthe conceptual injection situation of the injection solution in thehuman skin structure in accordance with the pressure transition based onthe two pressurizing modes as described above. In the first pressurizingmode performed in the minute time Δt (time ranging from the applicationof electricity in the initiator 20 to the arrival at the waitingpressure Pw2), as shown in FIG. 5A, a minute amount of the injectionsolution is allowed to inject from the syringe 1. In the injection ofthe minute amount of the injection solution, the energy amount, which ispossessed by the injection solution allowed to inject depending on theinjection amount per unit time, i.e., the injection flow rate, isdetermined by Expression 1 as follows.P=1/8•πρD ² u ³  (Expression 1)P: energy of discharging injection solution, p: density of injectionsolution, D: diameter of nozzle 4, u: discharging velocity of injectionsolution.

It is noted that Expression 1 merely calculates the energy amountpossessed by the injection solution allowed to inject. Even when onlyExpression 1 is provided, it is insufficient to explain the adjustmentof the injection depth in the skin structure. That is, in order toadjust the injection depth, it is necessary to perform the pressurecontrol according to the present invention. In view of the above, anexplanation will be made below about the pressure control according tothe present invention in relation to the adjustment of the injectiondepth in the skin structure while taking Expression 1 intoconsideration.

In the first pressurizing mode, the pressure transition, in which thepressure arrives at the waiting pressure via the peak pressure P1maxfrom zero, is performed in the extremely short period of time.Therefore, it is also affirmed that the injection solution having thehigh energy is allowed to inject to the skin in this process. As aresult, the injection solution, which is allowed to inject in the firstpressurizing mode, penetrates through the outermost surface of the skin,and the injection solution erodes the inside of the skin (discharginginjection solution is represented by S1 in FIG. 5A). In this situation,it is considered that the injection depth is more deepened as the energyof the discharging injection solution in the first pressurizing moderepresented by Expression 1 is more increased. In this context,according to Expression 1, the energy P of the discharging injectionsolution is proportional to the product of the cube of the dischargingvelocity u of the injection solution and the density of the injectionsolution. Therefore, the larger the peak pressure P1max is, the largerthe energy P of the discharging injection solution is. Further, theshorter the minute time Δt for the execution of the first pressurizingmode is, the smaller the energy P is. Therefore, the injection depth, atwhich the injection solution can arrive in the skin, can be adjusted byadjusting the energy P. FIG. 5A schematically shows the situation inwhich the injection solution arrives at the layer portion of theepidermis in the human skin structure. However, when the energy amountis adjusted, then the injection depth can be made deeper in the firstpressurizing mode, or the injection depth can be made shallower.

In this context, the waiting pressure, at which the pressure arrives inthe first pressurizing mode, is such a pressure that the erosion, whichis caused by the discharging injection solution in the firstpressurizing mode in the injection depth direction at the inside of theskin structure, is mitigated, and the diameter of the penetratingpassage can be reduced or shrunk at a part of the penetrating passagefor the injection solution formed in the skin structure. In this case,when the pressure is raised to the peak pressure P1max and the pressureis thereafter lowered to the waiting pressure, then the energy amountpossessed by the injection solution is lowered. Therefore, the erosionof the skin caused by the injection solution is mitigated, and thedischarging injection solution does not arrive at the deepest portion ofthe skin structure. Further, the skin structure of the living body has acertain elastic force. Therefore, on account of the elastic force, thediameter of the penetrating passage may be reduced or contracted by theelastic force while including the injection solution or scarcelyincluding the injection solution at a part of the penetrating passagehaving been already formed, especially on the forward end side (deepside in the depth direction). As a result, the state, in which thediameter is reduced, is formed on the forward end side of thepenetrating passage, and the state, in which the diameter is notreduced, is maintained on the proximal end side of the penetratingpassage, at the point in time at which the pressure arrives at thewaiting pressure in the first pressurizing mode. Therefore, thedifference in strength with respect to the pressure of the injectionsolution is generated between the forward end side and the proximal endside of the penetrating passage. That is, the strength is relativelyhigh on the forward end side of the penetrating passage as compared withthe proximal end side thereof. As a result, when the pressurization isperformed again in the second pressurizing mode as described later on,then the pressure of the injection solution is uniformly applied to theentire penetrating passage, but the penetrating passage portion, whichis in the unreduced diameter state, has the strength weaker than that ofthe reduced diameter portion, because the penetrating passage portion inthe unreduced diameter state is relatively enlarged or expanded. It isconsidered that this situation contributes to the diffusion of theinjection solution. According to the above, it is desirable that thewaiting pressure is the pressure which is lowered from the peak pressureP1max in the first pressurizing mode to such an extent that the forwardend side of the penetrating passage is contracted or shrunk by theelastic force exerted from the skin structure in the second pressurizingmode as described later on, i.e., to such an extent that the differencein strength of the penetrating passage, which can secure or guaranteethe diffusion of the injection solution in accordance with the secondpressurizing mode, is generated. For example, it is preferable that thewaiting pressure is not more than 50% of the peak pressure P1max.

In the next place, the pressure transition, in which the pressure israised from the waiting pressure Pw2 to the second peak pressure P2max2,is depicted in the second pressurizing mode. When the pressure of theinjection solution is raised again in accordance with the secondpressurizing mode from the state in which it is estimated that thedifference in strength is generated in the penetrating passage formed bythe injection solution owing to the arrival of the pressure of theinjection solution at the waiting pressure Pw2 in accordance with thefirst pressurizing mode, it is considered that the injection solution,which is confined in the penetrating passage having the reduceddiameter, is pressurized again. However, the injection solution, whichis allowed to inject in the second pressurizing mode, behaves topressurize the skin structure by the aid of the injection solutionexisting at the unreduced diameter portion rather than to directly acton the bottom of the penetrating passage, on account of the differencein strength as described above. Therefore, the injection solution causesthe permeation into the interior of the skin structure from thepenetrating passage in the unreduced diameter state, rather than thefurther erosion in the depth direction. In other words, it is consideredthat the injection solution is diffused to the interior of the tissue ofthe skin structure via the portion of the penetrating passage in theunreduced diameter state which is considered to have the relatively lowstrength with respect to the pressure (in FIG. 5B, the injectionsolution, which is diffused in accordance with the second pressurizingmode, is represented by S2). Further, the pressure increase rate, whichis provided in the second pressurizing mode, is gentler than thepressure increase rate which is provided in the first pressurizing mode.Therefore, the injection solution can be diffused into the skin alongthe extending direction of the layered tissue of the skin structurewithout uselessly deepening the injection depth of the injectionsolution. FIG. 5B shows the diffusion state as described above merelyconceptually. When the injection depth is set to any different depth asviewed in FIG. 5A, the diffusion state differs as well. For example, itis also possible to effect the diffusion so that the injection solutionis permeated into a portion disposed nearer to the dermis or into thedermis.

The period of time, in which the second pressurizing mode is continued,is determined depending on the amount of the injection solution(injection amount) allowed to inject by the syringe 1. After the passageof the second peak pressure P2max2, the pressure, which is applied tothe injection solution, is gradually lowered. However, the pressurebecomes zero at the point in time at which the injection solutionallowed to inject from the nozzles 4 is exhausted, and the secondpressurizing mode comes to the end. The purpose of the secondpressurizing mode is to diffuse the injection solution to the desireddepth of the skin structure. Therefore, it is preferable that theinjection solution amount, which is allowed to inject from the syringe 1in the second pressurizing mode, is larger than the injection solutionamount which is allowed to inject in the first pressurizing mode. Thissituation can be sufficiently realized, because the first pressurizingmode is performed within the minute time Δt as described above.

In this way, in the case of the syringe 1 according to the presentinvention, the pressure transition advances such that the pressureundergoes the waiting pressure in the first pressurizing mode and theinjection solution is diffused in accordance with the secondpressurizing mode. Accordingly, the injection solution can be fed to thedesired depth in the skin structure. In particular, the pressurization,which is performed in the second pressurizing mode, is principallydirected to the diffusion of the injection solution, and the injectiondepth is prevented from being uselessly deepened. Therefore, it ispossible to precisely diffuse the injection solution even at such aportion that the injection depth is relatively shallow.

An explanation will now be made about the pressure transitions L1, L2,L3 shown in FIG. 4 respectively. In these pressure transitions, the peakpressures, which are provided in the first pressurizing mode, areapproximately P1max and coincident with each other by utilizing the sameinitiator 20. The waiting pressures are dispersed in a range of Pw1 toPw3. However, as described above, as for the waiting pressure, when thepressure is lowered to some extent from the peak pressure in the firstpressurizing mode, then the erosion caused by the discharging injectionsolution in the first pressurizing mode, which occurs in the injectiondepth direction at the inside of the skin structure, is mitigated, andthe pressure may behave such a pressure that the diameter of thepenetrating passage can be contracted or reduced at the part of thepenetrating passage for the injection solution provided in the skinstructure. In this way, even when the same initiator 20 is used, the gasgenerating agents 30, each of which is arranged in the combustionchamber 9, have the different amounts. Accordingly, the pressuretransitions in the second pressurizing mode are changed as shown in FIG.4. Specifically, in the case of the pressure transition L1, the amountof the gas generating agent 30 is maximized. In the case of the pressuretransition L3, the amount of the gas generating agent 30 is minimized.In the case of the pressure transition L2, the amount of the gasgenerating agent 30 is the intermediate amount. Therefore, the peakpressures in the second pressurizing mode reside in a relationship ofP2max1 in pressure transition L1>P2max2 in pressure transition L2>P2max3in pressure transition L3. According to the three types of the pressuretransitions as described above, it is possible to provide the differentspeeds to diffuse the injection solution and the different amounts ofthe injection solution to be diffused at approximately the sameinjection depth.

The peak pressure P2max3, which is provided in the pressure transitionL3, has the value which is lower than that of the peak pressure P1maxprovided in the first pressurizing mode. In this procedure, the pressuredifference between P1max and P2max3 is within a predetermined ratio withrespect to P1max. This is because it is intended to clarify the pressuretransition in which the injection solution is diffused in accordancewith the second pressurizing mode after undergoing the waiting pressurein the first pressurizing mode, unlike any pressure transition based onthe conventional technique, in order to feed the injection solution tothe desired depth in the skin structure. The predetermined ratio isexemplified by 60% of P1max.

The peak pressures P2max1, P2max2, which are provided in the secondpressurizing mode in the pressure transitions L1, L2, have the valueswhich exceed the peak pressure P1max provided in the first pressurizingmode. The peak pressures P2max1, P2max2 as described above areappropriately set in order to realize the desired injection amounts.

The foregoing embodiment is explained assuming that the human skinstructure is used. However, the syringe according to the presentinvention can be used as the syringe for animals (for example, farmanimal, pet or the like) other than human. In this case, the type andthe amount of the ignition charge 22 carried on the initiator 20 and thetype and the amount of the gas generating agent 30 are appropriatelyadjusted while considering the characteristic of the skin structure ofthe injection target, for example, the Young's modulus or the like.

In the foregoing embodiment, the pressure is applied to the injectionobjective substance in the syringe 1. However, it is also allowable thatthe injection objective substance is, for example, a powder or agranular solid, provided that the injection objective substance can beallowed to inject from the syringe 1.

EXAMPLES

Experimental conditions and experimental results will now be describedbelow in relation to injection experiments (Experiments 1 to 4)performed by using the syringe 1 according to the present invention. Thefollowing experimental conditions were set in order to diffuse theinjection solution intensively or in a concentrated manner into the skinlayer of a pig as an injection target.

<Experimental Conditions>

(About Syringe 1)

87 mg of ZPP (zirconium and potassium perchlorate) mixture was used forthe ignition charge 22 of the initiator 20, and single base propellantin an amount shown in Table 1 below was used for the gas generatingagent 30. The diameter of the nozzle 4 is 0.1 mm, and the three nozzles4 are arranged concentrically.

The component ratio of the single base propellant is as follows.

Nitrocellulose: 98.1% by weight;

Diphenylamine: 0.8% by weight;

Potassium sulfate: 1.1% by weight;

Graphite (loss ratio (outage)): minute amount.

(About Injection Target)

In this embodiment, a skin portion of abdomen of a pig was used as theinjection target. Specifically, the pig was sacrificed, and then theskin portion was peeled off, followed by being stored for 6 days in aphysiological saline solution at 4° C. to prepare a sample (cooled andstored), or followed by being frozen and stored at −70° C. and thawedthereafter to prepare a sample.

(About Injection Solution)

In order to easily grasp the diffusion situation of the injectionsolution after the injection, a colored aqueous solution (methyleneblue) was used.

TABLE 1 Experi- Experi- Experi- Experi- ment 1 ment 2 ment 3 ment 4Initiator ZPP ZPP ZPP ZPP Amount of 87 mg 87 mg 87 mg 87 mg ignitioncharge Amount of gas Single base Single base Single base Single basegenerating propellant propellant propellant propellant agent 150 mg 90mg 180 mg 150 mg Injection target Frozen pig Cooled pig Cooled pigCooled pig<Experimental Results>

Next, the experimental results as obtained in accordance with theforegoing experimental conditions are shown below. FIG. 6A shows a viewillustrating a pig skin surface in relation to an injection result inExperiment 3 and a sectional view thereof (cross section taken alongAA). On the other hand, FIG. 6B shows a view illustrating a pig skinsurface in relation to an injection result in Experiment 4 and asectional view thereof (cross section taken along BB). Further, FIG. 6Cshows graphs illustrating the pressure transitions applied to theinjection solution in Experiment 1 to Experiment 4 respectively. Table 2shown below summarizes the predetermined pressure values in the pressuretransitions and the times required to arrive at the pressuresrespectively. The pressure, which was applied to the injection solution,was measured by using an electrostrictive element (piezoelectricelement) at a detection frequency of 100,000 times per second, i.e.,every 0.01 millisecond. The maximum pressure, which was detectedimmediately after the operation of the initiator 20, was adopted for thefirst peak pressure shown in Table 2 below. An average value of the datawas adopted for the waiting pressure, the data including the data asobtained within 0.05 ms before and after the minimum pressure (i.e.,pieces of data obtained at respective five points provided therebeforeand thereafter) recorded in such an interval that the pressure waslowered from the first peak pressure during the period in which the gasgenerating agent 30 was completely ignited after the operation of theinitiator 20. The maximum pressure, which appeared after the arrival atthe waiting pressure, was adopted for the second peak pressure. Therespective times required to arrive shown in Table 2 mean the periods oftime required until arrival at the respective pressures by using, as thestart point, the point in time at which the ignition current was allowedto flow to the initiator 20.

TABLE 2 Exp. Exp. Exp. Exp. 1 2 3 4 First peak pressure (MPa) 16.8 17.518.0 17.4 Time required to arrive at first peak 0.61 0.60 0.61 0.61pressure (ms) Waiting pressure (MPa) 6.73 7.39 8.95 8.84 Time requiredto arrive at waiting 1.73 1.74 1.71 1.74 pressure (ms) Second peakpressure (MPa) 15.1 15.4 32.3 29.2 Time required to arrive at secondpeak 17.29 18.19 13.61 14.60 pressure (ms) Waiting pressure ratio(waiting pressure/ 0.40 0.42 0.50 0.51 first peak pressure)

The foregoing experimental results are analyzed as follows. That is, inExperiments 1, 2, and 3, the injection solution, which was allowed toinject from all of the three nozzles 4 provided for the syringe 1, wassuccessfully diffused at the desired injection depth in the skin layerof the pig. For example, as shown in FIG. 6A corresponding to Experiment3, as overlooked from the skin surface, it is appreciated that theinjection scars are spread in approximately identical sizes at threepositions. In the cross section, the injection solution is not uselesslyspread to the fat layer and the muscle layer, and the injection solutionis diffused in a state of staying in the skin layer. If the injectionsolution is vaccine, the vaccine can be fed and diffused intensively orin a concentrated manner to the area in which it can be expected tocause the effective antigen-antibody reaction. Also in Experiments 1 and2 which are not shown, the effective diffusion of the injection solutionwas successfully confirmed in the same manner as in Experiment 3 shownin FIG. 6A.

On the other hand, in Experiment 4, as for the injection solutionallowed to inject from one nozzle of the three nozzles 4, the injectionsolution is somewhat spread to the fat layer and the muscle layer unlikeExperiments 1 to 3 (see a sectional view shown in FIG. 6B correspondingto Experiment 4). Further, as overlooked from the skin surface shown inFIG. 6B, it is acknowledged that the size of the injection scarcorresponding to the sectional view is smaller than those of theinjection scars formed at the other two positions. This is because theinjection solution arrived at the deeper position of the injectiontarget as shown in the sectional view in relation to the small injectionscar, and the amount of the injection solution, which was successfullyconfirmed from the surface, was decreased. However, although not shown,the effective diffusion of the injection solution was successfullyconfirmed for the two nozzles other than the nozzle shown in FIG. 6B inthe same manner as in Experiments 1 to 3.

Based on the foregoing fact, it is affirmed that when the waitingpressure ratio (defined as the value obtained by dividing the waitingpressure by the first peak pressure) has the value lower than thepredetermined value, the injection solution, which is allowed to injectfrom at least any one of the nozzles 4, can be effectively diffused intothe skin layer of the pig, wherein it is possible to find out thesignificance of practical use. More preferably, when the waitingpressure ratio is not more than 0.50, it is considered that theeffective diffusion is realized for the injection solution allowed toinject from all of the three nozzles 4 as shown in Experiments 1 to 3.In the case of any conventional needle-free syringe, the injectionsolution has been fed to the deep inside of the injection target to suchan extent that the injection scar cannot be confirmed even by beingoverlooked from the skin surface unlike the present invention. Takingthis fact into consideration, it is affirmed that the syringe 1according to the present invention provides the useful effect which canbe never realized by the conventional needle-free syringe.

Other Examples

According to the syringe 1, for example, cultured cells or stem cellscan be seeded or inoculated with respect to cells or scaffold tissue(scaffold) as the injection target in the field of the regenerativemedicine, other than the case in which the injection solution isinjected into the skin structure as described above. For example, asdescribed in JP2008-206477A, it is possible to inject, by the syringe 1,cells which may be appropriately determined by those skilled in the artdepending on the portion subjected to the transplantation and thepurpose of the cell regeneration, for example, endothelial cell,endothelial precursor cell, myeloid cell, preosteoblast, chondrocyte,fibroblast, skin cell, muscle cell, liver cell, kidney cell, intestinaltract cell, and stem cell, as well as every cell considered in the fieldof the regenerative medicine. More specifically, a solution (cellsuspension) containing the cells to be seeded or inoculated as describedabove is accommodated in the through-hole 14 by using the sealingmembers 7, 8, for which the pressurization is performed in accordancewith the pressure transition based on the first pressurizing mode andthe second pressurizing mode as described above. Accordingly, thepredetermined cells are injected and transplanted to the portionsubjected to the transplantation.

Further, the syringe 1 according to the present invention can be alsoused to deliver DNA or the like, for example, to cells or scaffoldtissue (scaffold) as described in JP2007-525192W. In this case, it ispossible to suppress the influence exerted, for example, on cellsthemselves or scaffold tissue (scaffold) itself when the syringe 1according to the present invention is used, as compared with when thedelivery is performed by using any needle. Therefore, it is affirmedthat the use of the syringe 1 according to the present invention is morepreferred.

Further, the syringe 1 according to the present invention is alsopreferably used, for example, when various genes, cancer suppressingcells, or lipid envelops are directly delivered to the objective tissueand when the antigen gene is administered in order to enhance theimmunity against the pathogen. Other than the above, the syringe 1 canbe also used, for example, for the field of the medical treatment forvarious diseases (field as described, for example, in JP2008-508881 andJP2010-503616) and the field of the immunological medical treatment(immunotherapy) (field as described, for example, in JP2005-523679). Thefield, in which the syringe 1 is usable, is not intentionally limited.

What is claimed is:
 1. A syringe for injecting an injection objectivesubstance into an injection target area of a living body without usingany injection needle, the syringe comprising: an enclosing unit whichencloses the injection objective substance; an ignition device whichincludes an ignition charge and flows an ignition current so that theignition charge is combusted; a pressurizing unit which pressurizes theinjection objective substance enclosed in the enclosing unit; and a flowpassage unit which defines a flow passage so that the injectionobjective substance, which is pressurized by the pressurizing unit, isallowed to inject to the injection target area, wherein the pressurizingunit raises a pressure applied to the injection objective substance to apeak pressure for the injection objective substance to penetrate througha surface of the injection target area and then lowers the pressureapplied to the injection objective substance to a waiting pressurewithin 2 msec after the ignition current was allowed to flow to theignition device.
 2. The syringe according to claim 1, wherein thepressurizing unit raises the pressure applied to the injection objectivesubstance to the peak pressure and then lowers the pressure applied tothe injection objective substance to the waiting pressure within 1.7msec after the ignition current was allowed to flow to the ignitiondevice.
 3. The syringe according to claim 1, wherein the waitingpressure is not more than 50% of the peak pressure.
 4. The syringeaccording to claim 1, wherein the ignition charge is any one ofexplosive charges of an explosive charge containing zirconium andpotassium perchlorate, an explosive charge containing titanium hydrideand potassium perchlorate, an explosive charge containing titanium andpotassium perchlorate, an explosive charge containing aluminum andpotassium perchlorate, an explosive charge containing aluminum andbismuth oxide, an explosive charge containing aluminum and molybdenumoxide, an explosive charge containing aluminum and copper oxide, and anexplosive charge containing aluminum and iron oxide, or an explosivecharge composed of a combination of a plurality of the foregoingexplosive charges.